i have flown into lapas boliva. runway alt 13,300 per captain. it was uncomfortable about 10 minutes before landing. i was uncomfortable. we sat on ground for 1 hr. fa had oxygen bottles. transit pax wern,t invited. after take off, maybe 10 mins, i told fa that it seemed that we were at a high cabin altitude. she said she was ok & didn't see a problem. 5 mins later i asked her to ask the capt what our cabin alt was. she came back w/ 8000 ft. i don't know if it ever got any lower. next, i flew lga dal on aa f-100 50 seat, i was uncomfortable breathing. same thing on return dal-lga. in the meantime [obviously greenwich], i've flown in a king air w/ no pressuration @ 12500 ft & had no problem. also flew on dornier twin engine 18 pax in argintina in mar this yr. we were at 12500 or so and i was ok. on the bolivia thing, it was probably made worse because of time at altidude from mia. ihave no idea on the f100's. any idea's, thanks